Design Of A Bionic Variable Stiffness Spine And Its Application To Quadruped Robot

Traditional quadruped robots almost have rigid trunk. Because bionic quadruped robots with rigid trunk can’t utilize the function of spine that is quadruped mammal’s important mechanism, they aren’t able to realize agile dynamic motion and high speed gallop.When quadruped mamml such as cheetah runs fast, it utilizes its flexible spine with bend to realize high speed dynamic motion. Meanwhile when cheetah makes a turn, its compliant spine deflects. Under these enlightenments of biology observation, this dissertation puts forward a kind of quadruped robot bionic spine which has variable stiffness and apply it on a quadruped robot DCat Ⅱ. Adjusting stiffness of bionic spine on pitch and yaw direction can improve robot’s speed and agility. The main work of this dissertation are as follows:Based on the observation of cheetah’s body structure and trunk motion feature, the dissertation presenst a kind of quadruped robot bionic spine which has variable stiffness. Bionic spine has three parts:lumbar vertebrae, thoracic vertebrae and sacral vertebrae. Each part consists of rigid vertebra and compliant intervertebral disc with different thickness. Both vertebra and intervertebral disc has four-leaf clover section. Meanwhile, this dissertation designed a stiffness adjustment mechanism according to screw drive mechanism. Test of static stiffness feature of bionic spine was accomplished.The pseudo rigid body model of bionic spine was build using knowledge of compliant mechanism aim at the bionic spine, and mechanic feature of bionic spine was analyzed. Meanwhile finite element analysis of the bionic spine was carried on.Quadruped robot DCat’s mechanical structure was reformed, and control software of DCat Ⅱ was established. Finally experiments were designed to study the influence of the bionic spine to foot-force, speed and turning radius.Experiment results showed that bionic spine can decrease foot-force of robot. Quadruped robot DCat Ⅱ can increase stride length by utilizing the bend of bionic spine to realize high speed dynamic motion. Meanwhile, DCat Ⅱ can realize turning motion through reasonable selection of the stiffness value of the bionic spine on yaw direction.